Abnormal photon absorption behavior in melanin detected by photothermal lensing due to simultaneous irradiation with multiple laser wavelengths

A photophysical model for describing the absorption of light by melanin bas ed on the mechanisms of sequential two-photon absorption is investigated. T he process involves a conversion of the photon energy in a photochemical ef fect such as photodissociation of the biological molecules. The collinear p hotothermal tensing technique is employed to obtain stable, reliable and ac curate detection of nonlinear photon absorption in melanin. In these experi ments, a He-Ne laser and an argon-krypton ion laser are used to provide two different excitation wavelengths simultaneously. The experimental results were consistent with the theoretical model described. (C) 2001 Society of P hoto-Optical Instrumentation Engineers.